JPS5947731A - Automatic focusing mechanism of projection exposing apparatus - Google Patents

Abstract

PURPOSE:To realize automatic focusing in exposure of pattern to be exposed in the order of lmum or sub-micron order by detecting a plurality of positions such as periphery and center of the exposing area of sensitive surface, executing arithmetic operation on the basis of respective data and thereby correcting relative position of object. CONSTITUTION:A wafer 3 on which main surface a resist 4 is applied is placed on a stage 5 of contaction and projection exposing apparatus, an optical system is provided to the stage 5, a pattern of reticle 1 loaded is contracted to 1/10 and is focused on the sensitive surface of resist of wafer 3. A photo detecting mechanism 8 detects the height of sensitive surface of the center region 10 and four corners 11 of single exposing area. Difference of height of sensitive surfaces appears as difference of light receiving areas of photo sensor 16 and the light sensing area 13 sends positional information of each sensor 16 to a control part 7. The control part 7 executes arithmetic operations in accordance with positional data received, a variety of data input to the control part 7 and operation routines, and five positions of single exposing area 9 respectively obtain height of stage located in the focal depth of optical system 2 and correct a stage 5 to the desired position through a driving part 6.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an autofocus mechanism in a projection exposure apparatus, particularly in a reduction projection exposure apparatus.

One of the first steps in the manufacture of semiconductor devices is to form a mask pattern made of resist on the main surface of a semiconductor thin plate called a wafer, and then use this mask pattern to diffuse impurities into the exposed area or to perform etching. There are 9 steps that I went through.

The mask pattern covers the entire main surface ν,! After fully coating the resist (photoresist), it is formed (20°C) by developing the partial areas such as Y, A, and G. As shown in FIG. 1, as one of the resist partial exposure devices 2, a 1/IO pattern f of the reticle 1 is blown and coated onto the wafer 3 with neo or resist. The image is formed on a part of the photosensitive surface (upper surface) of No. 4. In this state, the exposure processing tray is carried out. Then, the five stages on which Ueno and No. 3 are placed are sequentially moved by one step, and the exposure area is sequentially moved. Photosensitivity: quiet, partial sensation of entire area of one wafer ->'t,
This depends on the known reduction projection exposure apparatus.

By the way, such a reduction projection exposure force', focusing in the apparatus r (-4 exposures) is 10 m'-
'A mechanism that automatically focuses the whole area of a single exposure area using a micrometer, and the light emitted from the Pc source diode in the center of the single exposure area? f 11<i, all of the reflected light is received and the position of the photosensitive surface of the wafer is if! ('i
A mechanism that automatically focuses while detecting the object is generally known.

On the other hand, the mask pattern width tends to become finer as semiconductor devices become more highly integrated and smaller.
f)' 1 pm or submicron, the depth of focus of the exposure optical system is, for example, around ±111 m. Therefore, due to warping of the wafer, incurable filling of the resist, etc., the above-mentioned automatic focusing mechanism cannot always focus on the entire single exposure area.

Specifically, in the former air micrometer mechanism, if the exposure area is close to the periphery of the wafer, air leaks and detection becomes inaccurate. When air is sprayed onto the photosensitive surface, the water contained in the air is supplied to the resist, which may cause the resist to change due to chemical reactions and the photosensitive pattern to change. It was also found that a phenomenon occurs when the condition becomes more favorable. In addition, the latter photodetection mechanism detects with a spot light whose center mk vertical and horizontal lengths of the 10-cut exposure area are 3111111.100 μm, so this area and the nearby area are focused, but this spot light In areas far away from the irradiation area, the focus order will not necessarily match.

These out-of-focus areas may be due to wafer warpage or non-uniformity of the resist thickness, but depending on the characteristics of the area, the above-mentioned correction position adjustment using the By slightly shifting the
Conversely, it is also possible to cover the entire light area and bring it within the depth of focus of the optical system.

Therefore, the purpose of the present invention is to develop an autofocus Q47't in a reduction projection exposure apparatus that enables automatic focusing even in exposure patterns on the order of microns, such as t'', l, pm, or t. There is much to offer.

In order to achieve such an object, the present invention focuses a reticle pattern on the photosensitive surface of an article by using an optical system.
In an autofocus mechanism used in a projection fogging device that performs fC post-exposure, V! The location of the location of the object is detected by the 4th, 3rd, 3rd, 3rd, 3rd, 3rd, 3rd, 3rd, 3rd, 4th, 3rd, 4th, 3rd, 4th, 4th, 3rd, 3rd, and 3rd, based on these pieces of information, and are processed in the lft 1 section to determine the relative position of the object. The present invention will be described below with reference to Examples.

FIG. 2 is a schematic diagram showing an autofocus mechanism in a reduction projection N-light device t according to an embodiment of the present invention, and FIG. 3 is a plan view of a wafer having a photosensitive surface. resist 4
The wafer 3 coated on its principal surface is mounted on the stage 5 of a reduction projection exposure apparatus, as shown in No. 2 (9).

Optical system 2 is placed on stage 5, and the pattern of reticle 1 loaded with n1 weighs 1710 kg! The image is made smaller so that an image can be formed on the photosensitive surface which is the upper surface of the resist of the wafer 3. The stage 5 is moved by a drive unit 6 in horizontal plane XY directions and up and down. The operation of the drive section 6 is controlled by a control section 7 consisting of a microcomputer or the like.

On the other hand, this apparatus is also provided with a photodetection mechanism 8 for detecting the position of each part of the exposure area. One of the single exposure areas 9 in which a reticle pattern is irradiated onto the photosensitive surface of the wafer 3 by the optical system 2 is a part of the wafer 3, as shown in FIG. For example, l/
10" / single exposure area with projection exposure characteristics! ) - side length a rat 1 (This is a square area that is open. Therefore, as shown in FIG. central area 10 of
Detection of the photosensitive surface height (position @) of the inner area II at the four corners 1
-ru. That is, the original detector fff 8←j2 light projector 12
In the light projecting part 12, five projectors I4 emit spot light 15 to respectively cover 71 areas 10 in the single exposure area 9 and four corner areas 11 of Dr. A spot light 15 is irradiated onto the area. Five light receivers 16 are arranged in the light receiving section 13, corresponding to the light projectors 14 of the light projecting section 12.

The light reflected from the center/iu area io and the inner area 1-1 of the single exposure area 9 is received.

The difference in height 6 of the photosensitive surface is due to the difference in the light receiving position in the light receiver 16. Ru. Therefore, the position fW information of the light receiving unit 13←L each light receiver 16 is controlled [111 unit B? & and some.

The control unit 7 uses the sent position information, various information previously input to the control unit 7, calculation routines, etc. to determine the performance, position, and single exposure area 9.
The stage height at which each of the five positions in is within the depth of focus of the optical system 2 is determined, and the stage 5 is adjusted to a desired position by activating the drive unit 6. As a result, the entire area of the single exposure area 9 where exposure is started falls within the depth of focus of the exposure optical system 2, making it possible to clearly expose the reticle pattern. In addition, if a part of the single exposure area comes off the photosensitive surface of the sea urchin 3 due to the movement of the wafer 3, the wafer size information inputted in advance to the control section 7 will cause the part of the single exposure area to come off the photosensitive surface. The position information of the selected position is automatically deleted, and the height of the stage is determined based on the remaining position information.

In addition, in this example device, various types of information such as pattern dimensions and depth of focus of the optical system group to be changed and used are controlled in advance (
The selection of this work information is made by switching various switches on the operation panel prior to the exposure work.

With such an autofocus mechanism, even if the exposure pattern is minute, the entire exposure area is always within the depth of focus of the exposure optical system.11. can be done. As a result, the photosensitive yield is also improved.

Note that the present invention is limited to the above embodiment. shellfish. For example, the position measurement may be performed by transmitting and receiving ultrasonic waves instead of light, and the same results as in the previous example can be obtained.

As mentioned above, according to the present invention ↓11. If it's 171m or Q'
It is possible to provide an autofocus mechanism in a reduction projection exposure apparatus that can automatically bring the entire single exposure area within the focus of the optical system even when exposing an exposure pattern of submicron order.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing an outline of an exposure apparatus, FIG. 2 is a schematic diagram showing an autofocus mechanism in a projection exposure apparatus according to an embodiment of the present invention, and FIG. 3 is a plane view showing the detection position. It is a diagram. 1... Reticle, 2... Optical system, 3... Wafer,
4... Resist, 5... Stage, 6... Drive unit, 7... Control unit, 8... Light detection mechanism, 9... Single exposure area, 12... Light projecting unit , 13... Light receiving section, 1
5...Spot light.

Claims (1)

[Claims] ■, Reticle pattern acoustic optical system? An autofocus mechanism 1 in a projection exposure apparatus that performs image-forming exposure on the photosensitive surface of an article (the autofocus mechanism 1 detects all the positions of multiple locations such as the periphery and center of the exposure area on the photosensitive surface of the article, - An autofocus mechanism in an optical device for projection power characterized by being configured so that the relative position of the object is corrected by performing arithmetic processing in the control unit based on the seven-dimensional position.